1. Field of the Invention
The present invention relates to a fabricating method of fabricating a piezoelectric vibrating piece constituted by a piezoelectric material of quartz, lithium tantalate or the like, a piezoelectric vibrating piece fabricated by the fabricating method, a piezoelectric vibrator having the piezoelectric vibrating piece, an oscillator, an electronic apparatus and a radiowave timepiece having the piezoelectric vibrator.
Further, the invention relates to a wafer used in fabricating a piezoelectric vibrating piece and a jig for a wafer for holding the wafer.
2. Description of the Related Art
In recent years, a portable telephone or a portable information terminal apparatus uses a piezoelectric vibrator utilizing quartz or the like as a time source, a timing source of a control signal or the like or a reference signal source or the like. Various piezoelectric vibrators of this kind are known, for example, a piezoelectric vibrator having a piezoelectric vibrating piece of a tuning fork type, a piezoelectric vibrator having a piezoelectric vibrating piece of carrying out a thickness slipping vibration or the like is known.
Meanwhile, the piezoelectric vibrating piece is formed by a wafer (semiconductor wafer) made of various piezoelectric materials of quartz, lithium tantalate, lithium niobate and the like. Specifically, a wafer is polished to a predetermined thickness, thereafter, a plurality of outer shapes of piezoelectric vibrating pieces are formed by etching by a photolithography technology, and electrodes are formed by patterning respectively predetermined metal films to the plurality of piezoelectric vibrating pieces the outer shapes of which are formed. Thereby, a plurality of piezoelectric vibrating pieces can be formed from one piece of a wafer at a time.
Meanwhile, in fabricating a piezoelectric vibrating piece, it is general that first, the outer shape is formed, thereafter, pattering of a metal film or the like is carried out as described above (refer to JP-A-2006-148758). At this occasion, in order to fabricate a high quality piezoelectric vibrating piece, it is necessary to pattern metal films or the like accurately respectively to outer surfaces of the plurality of piezoelectric vibrating pieces outer shapes of which are formed. Therefore, it is requested to accurately position a wafer to a mask or the like. In this respect, in a background art, in working a wafer, it is a current state that a reference is constituted by an outer shape of the wafer.
However, the following problem remains yet.
First, in order to fabricate a piezoelectric vibrating piece by working a wafer, it is necessary that masks formed with various patterns are properly used in accordance with steps, and the masks are accurately positioned to the wafer at the respective times. For example, there are a case of patterning an electrode for vibrating a piezoelectric vibrating piece, a case of patterning a weight metal film 28 in order to adjust a frequency of a piezoelectric vibrating piece, a case of finally cutting respective piezoelectric vibrating pieces from a wafer and the like.
Meanwhile, in a background art, when a mask is positioned to a wafer, the mask is set by constituting a reference by the outer shape of the wafer as described above. Therefore, a quality of the piezoelectric vibrating piece is controlled by an accuracy of an outer shape of the wafer.
That is, although after forming a plurality of outer shapes of piezoelectric vibrating pieces at a wafer, it is necessary to accurately pattern respective electrodes, weight metal films 28 and the like, all of the outer shapes of wafers are not uniform but a more or less difference is necessarily brought about by the wafers. Therefore, when the mask is positioned to the wafer finished with forming the outer shape of the piezoelectric vibrating piece, a pattern of the mask does not coincide with the respective piezoelectric vibrating pieces and more or less deviation are frequently brought about.
Therefore, it is necessary to position the mask in consideration of the deviation, and therefore, time and labor is taken in positioning and an efficient operation cannot be carried out. Further, even in consideration of the deviation, high accuracy positioning is still difficult, and it is difficult to fabricate a high quality piezoelectric vibrating piece.